The present invention is related to a delivery system for self-expanding medical vascular devices.
Modern treatment of vascular blockage like arteriosclerosis in arteries or other abnormalities in anatomical ducts or vessels that create blockings or narrowing in the ducts, today more often comprises balloon dilatation and securing the inner vessel wall by means of metal grid cylinders, so called stents, to prevent collapse of the vessel walls after the dilatation. In other cases where there is a lesion in the duct wall causing bleeding or a risk of bleeding, covered stents or stented vascular grafts may secure such lesions.
Extremely important is the closure of such leaks in the vessels of the brain and the heart. Stents are also used to keep other ducts open in the body (e.g. the oesophagus, the bile ducts and the airway passages) that are suffering of blockages due to causes like cancer. There are also self-expanding covered stents or vascular grafts on the market. There are two main types of stents available, stents that have to be expanded by means of a balloon, i.e. pressure-expandable stents, and then the flexible self-expanding stents made of memory metals like the Nitinol stents, that will expand by themselves as a result of the inherent inner strength and memory.
The self-expanding memory metal stents have the advantage of taking the form and size of the vessel even some time after its placement and it remains flexible. The drawbacks of self-expanding stents and covered stents and covered stent grafts include the difficulty to deploy them. They will have to be restrained inside cylinders during the placement and thereafter pushed out of the restraining cylinders when the desired point is reached. The restraining cylinders and the pushing rods make the whole system bulky and stiff and thereby not suitable for small vessels and vessels on locations where the vessels are tortuous, like in the brain and in the heart.
However, U.S. Pat. No. 5,549,635 discloses a deployment apparatus for a self-expanding stent which uses a catheter, a balloon enclosing a distal part of the catheter, a self-expanding stent enclosing the balloon and two breakable retainer rings enclosing distal and proximal end portions of the self-expanding stent in a compressed state thereof. When inflating the balloon the retainer rings will get loose from the self-expanding stent which will expand. Then the catheter including the balloon and the breakable retainer rings should be withdrawn through the now expanded stent.
Since said retainer rings extend towards each other from the distal and proximal ends of the stent, there is a risk that the catheter cannot easily be withdrawn as a result of parts of the distal retainer ring being stuck between the expanded stent and the duct in which the stent is allowed to expand. Further, only a specific, substantially stiff self expanding stent may be used according to U.S. Pat. No. 5,549,635 which eliminates the use of said deployment apparatus in ducts of relatively small diameter and having a curved path and also eliminates the use of said deployment apparatus for deployment of several longitudinally spaced apart stents.
A main object of the present invention is to provide a stent delivery system and method which allow deploying of a self expanding stent also in ducts of relatively small diameters and following curved paths such that very bendable and flexible stents may be deployed.
Thus, a stent delivery system comprises a catheter having a distal end and a proximal end, and a self expanding stent device having a compressed state and an expanded state and being positioned along the catheter and close to the distal end thereof. The stent delivery system further comprises a capsule enclosing the self expanding stent device in its compressed state along substantially the whole length thereof, said capsule having an open distal end and a proximal end fixed to the catheter and further having at least one perforation extending longitudinally of said capsule from the distal end substantially to the proximal end thereof. Finally, the stent delivery system comprises a balloon positioned within the capsule so as to break the capsule along said at least one perforation. Thereby, the stent device may expand to its expanded state and the catheter with the broken capsule may be withdrawn.
In a first embodiment of the stent delivery system according to the present invention, the balloon encloses a distal part of the catheter and the stent device encloses the balloon.
In a second embodiment of the stent delivery system according to the present invention, the balloon encloses a distal part of the catheter and the stent device is positioned between the balloon and the capsule in a circumferentially limited area.
In a third embodiment of the stent delivery system according to the present invention, the balloon is positioned between the catheter and the capsule in a first, circumferentially limited area and the stent device is positioned between the catheter and the capsule in a second, circumferentially limited area.
In a fourth embodiment of the stent delivery system according to the present invention, the capsule is positioned outside the perimeter of the catheter. Then, the stent device and the balloon are preferably positioned side by side in the capsule. Alternatively, the balloon may be positioned within the stent device.
Further a stent delivery capsule device for introduction into a vessel by means of a catheter comprises a substantially cylindrical capsule having an open distal end and a closed proximal end, a self expanding stent device and a balloon, both positioned within the capsule and extending substantially along the length thereof.
Finally, a method of inserting a self expandable stent device into an anatomical duct, comprises the steps of
i)providing a stent delivery system which comprises: a catheter having a distal end and a proximal end, a self expanding stent device having a compressed state and an expanded state and being positioned along the catheter and close to the distal end thereof, and a capsule enclosing the self expanding stent device in its compressed state along substantially the whole length thereof. The capsule has an open distal end and a proximal end fixed to the catheter and further has at least one perforation extending longitudinally of said capsule from the distal end substantially to the proximal end thereof, and a balloon positioned within the capsule and capable of breaking the capsule along said at least one perforation when expanded;
ii) inserting the catheter to which the capsule is fixed, into said anatomical duct and to a desired position therein;
iii) inflating the balloon such that the capsule is ruptured and the stent device is expanded to its expanded state engaging an inner surface of the duct; and
iv) withdrawing the catheter and the capsule fixed thereto from said desired position in the duct,
whereby the stent device is deployed at the desired position in the duct.
The delivery system according to the invention can be made with small diameters. The system permits a more precise placement of the stent in the vessel than the prior systems relying on release from the system by pushing or movement in the axial direction of the catheter.
The delivery system according to the invention is also advantageous as compared to the delivery system of U.S. Pat. No. 5,549,635 in that it has a high flexibility and is soft so that it may enter tortuous vessels without damaging the vessel wall. Inside the capsule self-expanding devices with a great variety of forms may be used. Thereby tailored special devices having branches, ends sticking out, umbrella shape and any other shape may be restrained within the capsule during delivery. Further, the capsule may be produced together with the device as an integrated part thereof and later assembled to the catheter.